(a) Field of the Invention
The present invention relates to an apparatus for driving a plasma display panel and a method for displaying pictures on the plasma display panel. More specifically, the present invention relates to a plasma display panel driving apparatus that controls address consumption power and a method for displaying pictures on the plasma display panel.
(b) Description of the Related Art
Recently, flat panel display devices including a liquid crystal display (LCD), a field emission display (FED), and a plasma display panel (PDP) have been actively developed. The plasma display panel has higher luminance and light-emission efficiency and wider viewing angle than other flat panel display devices. Accordingly, the plasma display panel is being spotlighted as a display device replacing a conventional cathode ray tube (CRT).
The plasma display panel is a flat panel display that displays characters or images using plasma generated by gas discharge. The plasma display panel is constructed in a manner such that tens through millions of pixels are arranged in a matrix form depending on its size. The plasma display panel is classified into DC and AC types of display panels based on the form of a voltage waveform applied to the plasma display panel and the structure of a discharge cell.
In the DC plasma display panel, electrodes are not insulated but are exposed in a discharge space so that current flows in the discharge space while a voltage is applied to the plasma display panel. Thus, the DC plasma display panel requires a resistor for restricting the current. In the AC plasma display panel, electrodes are covered with a dielectric layer and thus a capacitance component is naturally formed to restrict current. Furthermore, since the electrodes are protected from collision of ions when discharge occurs, the life of the AC plasma display panel is longer than the life of the DC plasma display panel.
FIG. 1 is a partial perspective view of a conventional AC plasma display panel. Referring to FIG. 1, a scan electrode 4 and a sustain electrode 5 are formed in a pair on a glass substrate 1 and covered with a dielectric layer 2 and a protective layer 3. The dielectric layer 2 is coated on the back side of the scan electrode 4 and sustain electrode 5 to control a discharge current when discharge occurs and to facilitate generation of wall charges. The protective layer 3 is formed of MgO and protects the plasma display panel from a strong electric field. The plasma display panel includes a plurality of address electrodes 8 formed on a glass substrate 6, and an insulating layer 7 covering the address electrodes 8. Ribs 9 are formed in parallel with the address electrodes 8 on portions of the insulating layer 7, which correspond to regions between the address electrodes 8. A fluorescent material 10 is coated on the surface of the insulating layer 7 and both sides of each rib 9. The glass substrates 1, 6 face each other having a discharge space 11 between them. The scan electrode 4 and sustain electrode 5 are located perpendicular to the address electrodes 8 between the glass substrates 1, 6. A discharge space disposed at the intersection of adjacent address electrodes 8 and the pair of the scan electrode 4 and sustain electrode 5 forms a discharge cell 12.
FIG. 2 illustrates the arrangement of electrodes of the plasma display panel. Referring to FIG. 2, the electrodes of the plasma display panel are arranged in a matrix form. Specifically, address electrodes A1 through Am are arranged in a column direction and n scan electrodes Y1 through Yn and n sustain electrodes X1 through Xn are arranged alternately in a row direction. A discharge cell 12 shown in FIG. 2 corresponds to the discharge cell 12 of FIG. 1.
The AC type plasma display panel is operated through a reset period, an address period, and a sustain period. The reset period initializes the state of each cell to smoothly carry out an addressing operation. During the address period, an address voltage is applied to lit cells (addressed cells) to accumulate wall charges in order to discriminate the lit cells from cells that are not lit in the plasma display panel. During the sustain period, a sustain pulse is applied to the panel to generate discharge for displaying images on addressed cells.
When the plasma display panel is operated in the reset period, address period, and sustain period, the discharge space functions as a capacitive load and thus capacitance exists in the panel. Accordingly, reactive power for charge injection, which generates a predetermined voltage for the capacitance, is needed in addition to power for address discharge in order to apply an addressing waveform to the plasma display panel. Here, a larger amount of address power is consumed when address electrodes are frequently switched.
As described above, the address power is generated by switching of the address electrodes, which will now be explained in more detail.
FIG. 3 shows video data in the case of full white. Referring to FIG. 3, in the case of full white, all video data is 1 and thus there is little variation in data of address electrodes and there is a small number of pulse switching operations. Furthermore, charging/discharging reactive power is small because power consumption is increased in proportion to the number of switching operations. A driving waveform in this case is shown in FIG. 4. As shown in FIG. 4, one column indicated by a bold line in FIG. 3 is switched only once in the full white mode.
FIG. 5 shows dot pattern video data. Referring to FIG. 5, data is continuously changed from 1 to 0 and from 0 to 1 to result in many switching operations. A driving waveform in this case is shown in FIG. 6. As shown in FIG. 6, data of address electrodes is frequently changed and pulse switching of the driving pulse frequently occurs to increase power consumption in the case of the dot pattern video data.
As described above, the larger a difference between pixels of a previous line and pixels of a current line, the larger the number of switching operations. Consequently, power consumption is increased.